Modeling of caprock seal failure due to fluid injection

The past, present, and projected trends of increasing carbon dioxide (CO2) concentration levels in the atmosphere have raised serious concerns about global warming. Several efforts are being made to stabilize the current levels of CO2 emissions. Geologic sequestration of CO2 in deep saline aquifers is considered to be one of the potential options to reduce greenhouse gas emissions in the atmosphere. A tight, low-permeability caprock layer overlying the CO2-targeted reservoir limits the upward migration of CO2 and acts as a primary seal layer to trap CO 2. Large volumes of fluid or CO2 injected in the subsurface may over-pressurize the reservoir and increase the potential for mechanical seal failure. Such a scenario could lead to CO2 leakage with time.;In the present study, coupled single-phase and multi-phase fluid flow and geomechanical models were constructed to investigate the fluid flow and ground deformation behavior. Axisymmetric and three-dimensional fluid flow and deformation models were constructed. Coupled multi-phase fluid flow and deformation modeling was used to estimate the maximum sustainable injection pressure. Coupled multi-phase fluid flow and geomechanical models were also used to investigate the mechanical seal failure caused by CO2 injection. A parametric study was conducted on the geomechanical failure properties that cause shear failure in the caprock layer during CO2 injection. Parametric study of geomechanical properties such as cohesion, angle of friction and permeability show that these material properties have significant influence on shear failure of caprock layer. Also, finite element techniques were used to model shear failure of an inclined fracture or a fault zone during fluid injection. Results show the development of plastic strains when injected fluid migrates to the fault zone